Expression of apolipoprotein E in ballooned neurons-comparative immunohistochemical study on neurodegenerative disorders and infarction.

Apolipoprotein E (ApoE) in neurons is suggested to play crucial roles in neuronal degeneration and regeneration. We used antibodies against ApoE and phosphorylated neurofilament (pNF) to investigate the immunohistochemical features of ballooned neurons (BNs) in infarction and in various chronic degenerative disorders, including Pick body disease, corticobasal degeneration/progressive supranuclear palsy, Alzheimer's disease, and frontotemporal dementia. BNs in these chronic degenerative processes were intensely labeled with the anti-pNF as reported, whereas BNs in infarction showed less intense pNF-like immunoreactivity (IR). In addition, BNs in infarction were characterized by an intense ApoE-like IR. This ApoE-like IR was inconsistent or less intense in BNs in the chronic degenerative processes. The rarity of ApoE-positive glial cells in the vicinity of ApoE-positive BNs suggests that accumulated ApoE in BNs is generated in the neurons. Accumulation of ApoE in BNs in infarction may be linked to a regenerative process after acute transection of axons, which seems compromised in chronic degenerative processes.